How to sell free software

Many companies have tried to sell “free” software, with disastrous results (Here is a website dedicated to gnu license violations). There are some companies that willfully violate free software licenses, however, there are others that just don’t understand the license that was used and how it may effect future distribution.

The following is a list of the 3 most common open source licenses and a simple explanation of your distribution rights. This should give you an idea on if you are going to violate one of these distribution licenses, but you should always consult a lawyer if you are unsure.

BSD License

This is the most liberal license of them all and is very friendly regarding proprietary applications. If you get source code distributed under the BSD license, you can sell it in a proprietary application or redistribute your changes in an open source application.

There are a few variants of this license, but the following are the only requirements:

• A copy of the original license must be included
• The name of the author may not be used to endorse or promote products
  derived from this software without specific prior written permission

LGPL (GNU Lesser public license)

The LGPL is similar to the GPL, but allows you link to the licensed code from a proprietary application without having to give out all of the source code from the proprietary app. The only way you have to give out source code is if you modify the source of the original licensed code. This works well with libraries.

GNU License

you are allowed to use, redistribute, and change the software, but any changes you make must also be licensed under the GPL. This means that if you are using any GNU licensed code in your proprietary application, the source code of that application must also be released.

However, this does not mean you cannot make money with gnu licensed code.

Here are some ways:

• Give away the software and charge for support
• Use a free version (GNU licensed) as marketing for a paid version with more features
• Sell it, but only give the source away to anyone that purchases it (this can be considered a transfer fee).

One drawback with the last two methods is that your customers are legally allowed to redistribute/share your software and there isn’t much you can do about it.